Volvo Penta Outdrive rebuild or swap??

Have a buddy with a 97 Fourwinns bowrider. Has a 3.0L Mercruiser motor with a Volvo Penta SX Cobra outdrive. He says the outdrive blew the top end and screwed up the bottom end as well needs a full rebuild. I know nothing about boats. Have rebuild lots of motors but never got into boats. Would it be better to rebuild the outsdrive or swap it out for one?? Looking at the price of used working volvo outdrives of 5 grand seems like there is a better option. Wondering if you can put a Mercruiser outdrive on the boat?? There seems to be lots of them around. what all needs to be down to swap them out??